Damper winding for high speed salient-pole machines



u 1939 v R. A, BAUDRY 2,169,017

DAMPER WINDING FOR HIGH SPEED SALIENT POLE MACHINES Filed April 14, 1958K d RU Y m m m w VA T m,m H mm Patented Aug. 8, 1939 UNITED STATESDADIPER WINDING FOR- HIGH SPEED SALIENT-POLE MACHINES Rene A. Baudry,Pittsburgh, Pa., assignor to Westinghouse Electric & ManufacturingCompany, East Pittsburgh, Pa., a corporation of Pennsylvania ApplicationApril 14, 1938, Serial No. 201,952

8 Claims.

My invention relates to dynamo-electric machines having salient-polerotor members and damper windings disposed in the pole-face portions ofthe salient poles, and it has particular relation to large high-speedmachines of that type.

The particular object of the invention is to provide new and improvedmeans for taking up the centrifugal forces operating on the end rings ofthe damper windings and at the same time restraining, to a large extent,the distortions due to the excessive heating when the machine is beingstarted.

With the foregoing and other objects in view,

my invention consists in the combinations, structures and methodshereinafter described and claimed, and illustrated in the accompanyingdrawing, wherein: Figure 1 is a fragmentary cross-sectional View of alarge synchronous salient-pole machine embodying my invention, partsbeing broken away for clarity of illustration, the section-plane beingindicated by the line II in Fig. 2,

Fig. 2 is a fragmentary longitudinal sectional view of the machine, on asomewhat larger scale than Fig. 1, showing one end of the damperwinding, and

Fig. 3 is a fragmentary developed plan view of a portion of thedamper-ring construction with its associated steadying ring.

The drawing shows my invention applied, by way of example, to a largesynchronous machine having a primary-winding stator member I of usualconstruction, and a field-winding rotor member 2 having twelve salientpoles 3, so that the machine operates at 600 R. P. M. on 60 cycles,which is a fairly high speed for a machine of its size (60,000 kw.) thecentrifugal forces developed in the rotor member being quite highbecause of the large diameter, which is practically nine feet.

In the pole-face portions 4 of the salient poles 3 there are disposeddamper-winding bars 5, and the bars 5 of each salient pole are joined,at each of their ends, to a damper segment 6. The twelve damper segments6 at each end of the machine are joined by separate connectors l, whichare shown as comprising two flexible strips which are bent out of astraight line, as indicated at 8 in Fig. 3, so that when they expand andcontract due to heating, only a small stress will be produced in theflexible strips '1.

At each end of the machine, a strong ring 9 is mechanically associatedwith the segments 6 and connectors I, for taking up the centrifugalforces,

a and for resisting distortions due to the heating of the segments andconnectors. These parts are mechanically held together by a large numberof bolts H which are preferably provided with spacing washers I2, ofrelatively poor heat-conductivity, for spacing the ring 9 from thedamper segments 6 and from the connectors 1, so as to retard theheat-flow to the ring 9.

The damper segments 6, and the separate connectors 1 between thesegments, are of copper and are in good electrical connection with eachother, so as to constitute the end-rings for the damper bars 5, whichare also of copper. The supporting ring 9 is a heavy steel forging madein one piece, of a grade of steel preferably chosen for its high tensilestrength. It has a considerably higher resistivity than copper, so thatmost of the damping-current flows through the segments 6 and connectors1, rather than through the rings 9. The spacing washers 12 arepreferably made of a material having a low-heat conductivity, such as anickel-iron alloy, whereby the heat-transfer to the ring 9 is greatlyreduced. The iron rings 9 could be completely insulated from, thecurrent-carrying parts, but in general I find that the comparativeelectrical resistivities are such that practically all of thedamper-winding current is kept out of the ring 9, so that it is notnecessary to attempt to insulate the same.

When a machine of the size illustrated is started, the starting torquemust be supplied by the damper winding 5, 6 and 1. During the startingtime, which may be of the order of three minutes, the entire ultimatekinetic energy of the rotor must be transferred, in the form of heat, tothe damper winding. If it were not for heat-radiation, this stored heatwould raise all parts of the damper winding to a temperature of theorder of 900 C. With such heat-radiation as is present, the maximumtemperature of the damper bars 5 is something of the order of 400 C.,which means a lengthwise expansion of some threequarters of an inch in adamper bar 5 of about eight feet in length. Similar heat effects tend tocause expansion of the damper segments 6 and end-connectors 'l, andthese parts can expand somewhat circumferentially, but the iron ring 9prevents a movement in the radial direction, which would communicateitself to the ends of the damper bars 5 which are brazed to the dampersegments 6. I thus prevent the bar-ends from being bent or distorted tosuch an extent that breakage would occur after a certain number ofstartings and stoppings of the machine.

According to my invention, the damper segments 6 and the separateconnectors l are firmly supported against radial expansion due tothermal and centrifugal forces, which are really quite high in a machineof this size and speed, by means of the relatively cool steel ring 9, sothat the expansion of the ring 9 is quite low, resulting in acorresponding material curtailment of the possible bending stresseswhich can be applied to the ends of the damper bars 5.

While I have described my invention in a form of embodiment which is atpresent preferred, I wish it to be understood that such embodiment isintended only for illustrative purposes, and not by way of limitation.the appended claims shall be accorded the widest scope of interpretationpermitted by the prior art and by the language of the claims.

I claim as my invention.

1. A dynamo-electric machine having asalient pole rotor, damper-windingbars in the 'poleface portions of the salient poles, a damper segmentfor the bars at each end of each salient pole, separate connectorsbetween the several segments at each end of the machine, a strong ringat each end of the machine for taking upthe centrifugal forces and forresisting distortions due to heating of the segments and connectors, andmeans for mechanically associating the rings with their respectivesegments comprising connecting-means for preventing an easy directheattransfer between the rings and their respective segments.

2. A dynamo-electric machine having a salient-pole rotor, damper-windingbars in the poleface portions of the salient poles, a damper segment forthe bars at each end of each salient pole, separate connectors betweenthe several segments at each end of the machine, a strong ring at eachend of the machine for taking up the centrifugal forces and forresisting distortions due to heating of the segments and connectors, andmeans for mechanically associating the rings with their respectivesegments and connectors comprising connecting-means forvpreventing aneasy direct heat-transfer between the rings and their respectivesegments and connectors.

3. A dynamo-electric machine having a salient-pole rotor, damper-windingbars in the poleface portions of the salient poles, a damper segment forthe bars at each end of each salient pole, separate connectors betweenthe several segments at each end of the machine, a strong ring at eachend of the machine for taking up the centrifugal forces and forresisting distortions due to heating ofthe segments and connectors, andmeans for mechanically associating the rings with their respectivesegments comprising connecting-bolts between the connected parts, andspacing washers of a relatively poor heat-conductivity associated withsaid bolts between said connected parts.

4. A dynamo-electric machine having a salient-pole rotor, damper-windingbars in the poleface portions of the salient poles, a damper segment forthe bars at each end of each salient pole, separate connectors betweenthe several segments at each end of the machine, a strong ring at eachend of the machine for taking up the centrifugal forces and forresisting distortions due to heating of the segments and connectors, andmeans for mechanically associating the rings with their respectivesegments and connectors comprising connecting-bolts between theconnected parts, and spacing washers of a relatively poorheat-conductivity associated with said bolts between said rings and saidconnected parts.

5. A dynamo-electric machine having a salient-pole rotor, damper-windingbars in the poleface portions of the salient poles, a damper segment forthe bars at each end of each salient pole, separate connectors betweenthe several seg- I desire, therefore, that,

ments at each end of the machine, a strong ring at each end ofthe-machine for taking up the centrifugal forces and for resistingdistortions due to heating of the segments and connectors, and means formechanically associating the rings with their respective segmentscomprising connecting-means for preventing an easy direct heattransferbetweenvthe rings and their respective segments, the rings having ahigher resistance than the segments and connectors whereby most of'thedampingwinding current flows through the segments and connectors ratherthan the rings.

6. A dynamo-electric machine having a salient-pole rotor, damper-windingbars in the poleface portions of the salient poles, a damper segment forthe bars at each end of each salient pole, separate connectors betweenthe several segments at each end of the machine, a strong ring at eachend of the machine for taking up the centrifugal forces and forresisting distortions due to heating of the segments and connectors, and

means for mechanically associating the rings with their respectivesegments and connectors comprising connecting-means for preventing aneasy direct heat-transfer between the rings and their respectivesegments and connectors, the rings having a higher resistance than thesegments and connectors whereby most of the damping-winding currentflows through the segments and connectors rather than the rings.

'7. A dynamo-electric machine having a salient-pole rotor,damper-winding bars in the poleface portions of the salient poles, adamper segment for the bars at each end of each salient pole, separateconnectors between the several segments at eachlend of the machine astrong ring at each end of the machine for taking up the centrifugalforces and for resisting distortions due to heating of the segments andconnectors, and means for mechanically associating the rings with theirrespective segments comprising connecting-bolts between the connectedparts, and spacing washers of a relatively poor heatconductivityassociated with said bolts between said connected parts, the ringshaving a higher resistance. than the segments and connectors wherebymost of the damping-winding current flows through the segments andconnectors rather than the rings. 7

8. Aldyna'mo-electric machine having a salient-pole rotor,damper-winding bars in the poleface portions of the salient poles, adamper segment for lthe barsat each end of each salient pole, separateconnectors between the several segments at each end of the machine, astrong ring at each end of the machine for, taking up thecentrifugalforces and forrresisting distortions due to heating of thesegments and connectors, and means for mechanically associating therings with their respective segments and connectorscomprising-connecting-bolts between the connected parts, and spacingwashers of a relatively poor heat-conductivity associated with saidbolts between said rings and said connected parts, the

ringshaving a higher resistance than the seg- RENE A. BAUDRY.

